1. Field of the Invention
This invention relates to an electromagnetic driving device, and more particularly to the electromagnetic driving device that introduces a current magnetic field as a power source to drive an optical focus or zoom lens set, and whose lens set can be positioned by a friction induced by a field of magnets during a power-off state.
2. Description of the Prior Art
Referring to FIG. 1, an exploded view of a conventional focus lens set is shown. The focus lens set utilizes a mechanical focusing unit 9 including a hi-cost precision driving element 91 (for example, the step motor, the supersonic motor, the piezoelectric actuator, . . . , etc.) as the power source to drive the carrier 93 of the lens set 92, and many other transmission elements. Actually, such an arrangement in the conventional focus lens set, structural complication, assembly difficulty, cumbersome appearance and high cost are inevitable. Also, considerable energy consumption is another disadvantage for this type of lens sets. All of the foregoing features make the price of the aforesaid lens set irreducible.
In the early stage of the photography art, large human labor has been involved in metering, focusing and winding. Inevitably, it can be foreseen that how sorry would be if meeting a human mistake in taking photos in an important scene. Obviously, a quality photographer is the only answer to ensure photographing during such an important scene. Yet, it is well known that no 100% photographer is available anywhere and anytime. In the 50's and 60's, a great step has been achieved in the mechanical automation, from which people believe that automation would be the key to the future world. At that time, in the photography art, various developments such as the auto-metering device, the electrical winding apparatus and so on, have convinced people that automation is the future to the photography art. Among these developments, the development in the automatic focusing system who ensures the possibility of rapid photo-taking plays an important part.
Along with the technology development, conventional photographic apparatus has been progressed both in photographing quality and in the miniaturized appearance. However, the mechanical focusing lens set driven by the step motor hinders a further reduction in occupation of the apparatus
On the other hand, electromagnetic technology has also been introduced to improve the VCM electronic feedback system in monitoring the bias of the coil, which can replace the conventional step motor and provide a size down in the driving mechanism. Another development of the photography art is to add the photographic function to the other apparatus; for example, the integration of the photographic unit to the mobile phone, the PDA, the notebook computer and so on. All these changes make the current electronic merchandises equipped with a photographic unit that enhances a powerful video application to these aforesaid apparatuses.
Nevertheless, the aforesaid mobile phone, PDA, notebook computer, and the like portable electronic apparatus all have limitations in the battery capacity. Therefore, in aiming at the future of the photography art, the devotion upon how to design a low-energy-consumed driving device for focus or zoom lens set and how to anchor the lens set while the power is off is definitely welcome to the skilled person in the art.